This invention relates to color displays providing a plurality of colors for each pixel within the display. These displays may be used for pictures, information displays and panel data displays.
Prior art cathode ray tube color displays use additive color control. Three display spots, one for each primary color (red, green and blue), are required for each full color pixel on the display. This requires three beams of electrons, one for each of the three primary colors in a pixel. The display must have monochrome modulating devices for each of the three electron beams required to generate the colors.
Liquid crystal display devices used in multi-color displays have insufficient contrast, limited viewing angles and poor color capability. The poor color capability is true on segmented and dot matrix displays as well as on liquid crystal projected light valves for large screen displays. A major disadvantage of liquid crystal displays is the requirement for three separate channels, one for each primary color, to produce a full color display.
Certain organic and inorganic materials in electrochromic devices are capable of selective light absorption. White light passed through these materials forms a color image when unneeded frequencies are absorbed by the materials.
It is known that an electric field may be applied to a film of electrochromic material which is deposited between a transparent conductor and an aqueous electrolyte solution. This technique produces a blue or white display. It is also known that other color effects can be obtained with lutetiumdiphthalocyanine constructed in both opaque and translucent cell configurations. Colors ranging from rose through a somewhat neutral shade of gray, to green, blue-green, deep blue, and violet have been obtained by controlling the voltage applied to such materials.
Electrochromic light valves (ECLV) are known in the art. ECLVs have the capability of generating different colors within a single element when the voltage applied to the element is changed a few volts.
Light valves have become an important display technique for command and control display devices requiring large display areas and high brightness. However, light valves currently in use are not capable of producing multiple colors from a single pixel device. For full color display systems, three separate electrical and optical channels must be fabricated and combined to generate a composite picture. This approach requires additional space, weight, complexity, and cost. Also, these systems often require added maintenance to keep the three channels properly converged.
Display addressing is an important and vital part of any display device. For the projection displays, addressing by multiplexed circuitry and direct interfacing with display dot matrix material is not adequate. Active addressing is required for large displays. Unfortunately, if the active elements are placed on the display surface they take up part of the available display area. Loss of display area leads to limitations in resolution and brightness.